In a networked environment, email may be routed from a sending client over the network to one or more destination recipient mailbox servers. Conventional email routing involves routing an email message through mail transport agents or servers using simple mail transfer protocol (SMTP). Typically, when an email message passes through a mail transport agent, data associated with the email message may be only briefly stored on the mail transport agent for a period long enough to receive the email message from the sender and to send the email message to the next server on the email transmission route.
Email applications are widely used by users on a variety of client devices for non-real time correspondence. With the proliferation of computing and networking technologies, email use has become an inextricable part of daily personal and professional lives. The increased reliance on email brings with it the disadvantage of how to deal with increasingly large numbers of emails. It is a common occurrence to receive and transmit massive amounts of email through limited resources such as mail transport agents.
Typically, a substantial portion of email transmitted and received is unsolicited email (also known as spam). Legacy anti-unsolicited email protection technologies rely on existing knowledge of messaging factors such as sender, recipient, sender domain, IP address, and associated reputation. Reputation has a high value role in making a determination about a message being an unsolicited email. If reputation for message factors is not available, unsolicited email determination becomes a significant obstacle for protection technologies.